1. Field of the Invention:
The present invention relates to a strain gage-based weighing apparatus destined for use in a platform scale, material-feeding hopper, compression tester, tensile tester, etc.
2. Description of Related Art:
FIG. 1 is a plan view, and FIG. 2 is a front view, of a typical example of the conventional weighing apparatuses using strain gages. The weighing apparatus is generally indicated with a reference 100.
As will be best seen in FIG. 2, the weighing apparatus 100 comprises a fixing frame 101, a load receiver 102 having a cylindrical hole 102a formed in the center thereof, a plurality of beam members 103, upper and lower faceplates 104a and 104b, a cylinder 105, an flexible layer 106, strain gages 107, and a loading plate 108. The flexible layer 106 is made of rubber or resilient material and bonded by curing to and between the upper and lower faceplates 104a and 104b. The flexible layer 106 is formed like a disk. The flexible layer 106 is adapted to show dynamic characteristics such as compressive rigidity, flexural rigidity, etc. which are generally point-symmetrical in all directions through the disk center. The cylinder 105 is provided in the center of the lower faceplate 104b having the generally same disk-like shape as the flexible layer 106, and fitted in a circular hole 102a in the load receiver 102. The bottom surface of the load receiver 102 is positioned above a surface on which the weighing apparatus 100 is placed. The plurality of beam members 103 is disposed around the load receiver 102, and securely bonded to and between the load receiver 102 and fixing frame 101. Each of the strain gages 107 is secured to the lower side of each beam member 103 by attaching or otherwise. Thus, when a vertical load is placed on the upper faceplate 104a, it will push down the load receiver 102 via the flexible layer 106 and lower faceplate 104b to bend the beam members 103, thereby changing the resistance of the strain gages 107 on the beam members 103.
For a larger loading surface required for the weighing apparatus, a loading plate 108 is used, and one weighing apparatus 100 is disposed at each of the four corners of the loading plate 108 as shown in FIG. 3.
In these conventional weighing apparatuses, the flexible layer 106 is disposed between the upper faceplates 104a the load receiver 102 in such a manner that the latter can be moved horizontally and tilted in relation to each other.
When an object whose weight is to be measured is placed on the upper faceplate 104a or the loading plate 108, a shock will be produced to apply an external force to the weighing apparatus 100. The components of the weighing apparatus will thermally be contracted and the fixing holes may not possibly be formed precisely in some cases.
The above horizontal relative movability and tiltability of the upper faceplates 104a and the load receiver 102 are intended to accommodate such external force, thermal contraction, formation error, etc. in order to protect the weighing apparatus or weighing apparatuses.
However, the conventional weighing apparatuses are not advantageous as follows:
That is, when too large a vertical load is placed on the upper faceplate 104a or the loading plate 108, the flexible layer 106, if it has no sufficient hardness, will be compressed beyond its elasticity and thus cannot sufficiently accommodate the deformation of the upper faceplate 104a or loading plate 108 caused by the vertical load. For measuring such a large vertical load without any trouble, the flexible layer 106 should be of an increased hardness. As a result, however, the flexible layer 106 will be too stiff for the upper faceplate 104a or loading plate 108 to move horizontally and tilt. Namely, deformation caused by such horizontal movement and tilting will not possibly be accommodated to a sufficient extent.
Accordingly, the present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing a weighing apparatus capable of measuring a large vertical load and sufficiently accommodating deformations caused by horizontal movement and tilting.
The above object can be attained by providing a weighing apparatus comprising, according to the present invention, an apparatus body with strain gages, a load button to transmit a weight of an object to be measured to a loading surface of the apparatus body, a top plate on one side of which the load button is installed and to the other side of which the object weight is applied, an elastic member provided around the load button and between the loading surface and top plate, and connecting members to connect the top plate to the loading surface in such a manner that the top plate can move horizontally within a predetermined range and tilt about the load button and to prevent the top plate from coming out upward.
These objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.